British Prime Minister Theresa May declared the Manchester Arena attack a “callous terrorist attack” and “the worst attack the city has ever experienced.” May stressed that the attack was particularly cruel for targeting young people and that children are among the 22 casualties.

“We now know a single terrorist detonated his improvised explosive device, deliberately choosing the time and place to cause maximum carnage, to kill and injure indiscriminately,” May said outside 10 Downing Street, the prime minister’s official residence in London, amid flags at half-mast the morning after attack.

“This attack stands out for its appalling, sickening cowardice, deliberately targeting innocent and defenseless young people who should have been enjoying one of the most memorable nights of their lives.”

Just as thousands of pink balloons were cast into the arena as the finale of Ariana Grande’s concert, audience members heard a loud blast ripped outside the 21,000-seat venue. Police were reportedly called to the scene at 10:33 p.m. Greater Manchester Police reported early Tuesday morning that 22 people were confirmed dead, excluding the assailant. An additional 59 people were wounded and taken to eight hospitals in the city, some with life-threatening injuries, May said. Roughly 400 police officers were involved in the traumatic scene.

May will travel to meet Manchester today to meet with the head of police. She became prime minister in 2016 after a career as one of the longest-serving home secretaries. She is one of Britain’s most experienced politicians for dealing with terrorism and security.

The Manchester attack came two weeks before Britain’s June 8th general election, which May said in her speech, has been suspended. Britain is currently preparing to exit the European Union in two years.